(1) Field of the Invention
The present invention relates to information processing of data signals from ocean deployed acoustic buoy fields and more specifically to a system for improving the detection, classification and localization of undersea vehicles such as submarines, UUVs and the like using beamforming techniques on data from active and passive free floating acoustic buoys deployed in the ocean.
(2) Description of the Prior Art
A field of sonar buoys is often deployed at sea in order to acoustically detect, classify and localize the position of undersea vehicles. These buoys may be passive receivers or may be capable of receiving active acoustic transmissions in a bistatic or multistatic configuration. To-date, the usefulness of such buoy fields has been limited by the individual performance of each omnidirectional buoy.
FIG. 1 shows a prior art towed linear receiver array 10. Towed array 10 includes a linear series of hydrophones 12 sequentially attached to a central cable 14. Hydrophones 12 and cable 14 are enclosed within a hose 16 which is in turn filled with oil 18. A tow cable 20 is fixedly attached to one end of array 10 in order to pull the array through the water in the generally horizontal direction of tow 22. Well known line array beam forming techniques are used on the data from the array of hydrophones so as to achieve array gain and improve detection, localization and classification performance.
FIG. 2 shows a prior art volumetric towed array configuration 40 including a plurality of the towed arrays 10 of FIG. 1. Arrays 10 are fixedly attached in spaced apart relationship to a common tow body 42 so as to stream horizontally in parallel behind the moving tow body. The other end of tow body 42 attaches to tow cable 20 which pulls configuration 40 in the direction of tow 22. Multi-line linear towed array beamforming is then utilized to extract even more target location information than the single towed array of FIG. 1.
The prior art towed hydrophone arrays described above, while accurate in target detection, require tow induced movement in order to remain in a known horizontal plane. Other fixed sensor array types such as planar, spherical and cylindrical have known relative element spacing thereby permitting use of well known beamforming techniques for accurate target location. Stationary buoy fields on the other hand do not presently experience the benefits of such tow movement or fixed volumetric spacing.
What is needed is a way to make better use of the data collected from the multiplicity of stationary or slowly drifting acoustic sonar buoys deployed over a pre-selected ocean surface area, with each buoy having one or more sensors extending vertically downward from the underside of the buoy.